1. Field of the Invention
This invention relates to a digital electronic still-video camera as well as to a method of controlling the camera.
2. Description of the Related Art
In a digital electronic still-video camera, data compression is carried out in order to record image data, which represents the image of a subject, on a memory card in an efficient manner. The compressed data is decompressed in order that the image of the subject represented by the compressed image data may be displayed on a monitor display unit.
A digital electronic still-video camera can be set to take a sequence of pictures in addition to a single picture in the same manner as a conventional camera which records the image of a subject on silver halide film, thereby making rapid-sequence photography possible. In a digital electronic still-video camera, however, time is needed for data compression owing to the necessity for compression of the image data. As a result, the limit on rapid-sequence picture taking is on the order of three pictures in one second.
Accordingly, an object of the present invention is to provide a digital electronic still-video camera, as well as a method of controlling the same, in which rapid-sequence photography is possible at high speeds.
According to the present invention, the foregoing object is attained by providing a digital electronic still-video camera comprising image pick-up means for outputting image data, which represents the image of a subject, each time a picture is taken in a rapid-sequence photographic operation, an image memory for storing one frame of image data, first compressing means for compressing the one frame of image data, which is outputted by the image pick-up means, in such a manner that the amount of image data will become the reciprocal of a predetermined maximum number of frames capable of being photographed in rapid sequence, means for performing control in such a manner that the image data compressed by the first compressing means will be stored in an area of the image memory that conforms to the number of picture-taking operations in the rapid-sequence photographic operation, the image memory being segmented into a plurality of areas in accordance with the maximum number of frames capable of being photographed in rapid sequence, second compressing means for compressing the image data, which has been stored in the image memory, after the rapid-sequence photographic operation ends, and means for recording, on a recording medium, the image data compressed by the second compressing means.
Further, in accordance with the present invention, the foregoing object is attained by providing a method of controlling a digital electronic still-video camera, comprising a step of performing a first data compression, with regard to one frame of image data which represents the image of a subject obtained in each picture-taking operation of a rapid-sequence photographic operation, in such a manner that the amount of data will become the reciprocal of a predetermined maximum number of frames capable of being photographed in rapid sequence, a step of storing the image data, which has been compressed by the first data compression, in an area of the image memory that conforms to the number of picture-taking operations in the rapid-sequence photographic operation, the image memory being segmented into a plurality of areas in accordance with the maximum number of frames capable of being photographed in rapid sequence, a step of performing a second data compression with regard to the image data, which has been stored in the image memory, after the rapid-sequence photographic operation ends, and recording, on a recording medium, the image data compressed by the second compression.
The maximum number of frames capable of being photographed in rapid sequence may be decided permanently in advance or the maximum number of frames can be set at will from an input unit.
The end of the rapid-sequence photographic operation may be when the predetermined number of frames have been taken or when depression of a shutter-release button is released during the picture-taking operation.
The first compression may be performed by extracting (by means of thinning-out processing) one pixel of image data from image data of pixels the number of which is the maximum number of frames capable of being photographed in rapid sequence, or by creating one pixel of image data by averaging image data composed of pixels the number of which is the maximum number of frames capable of being photographed in rapid sequence.
Thus, in accordance with the present invention, a first compression is performed in such a manner that the one frame of image data outputted by the image pick-up means will become an amount of data which is the reciprocal of a predetermined maximum number of frames capable of being photographed in rapid sequence. The compressed image data is stored temporarily in an area of the image memory that conforms to the number of picture-taking operations in the rapid-sequence photographic operation, the image memory being segmented into a plurality of areas. All of the image data thus temporarily stored is subjected to a second compression and then recorded on the recording medium.
In accordance with the invention, the arrangement is such that prior to the compression of image data and recording of the compressed image data on the recording medium, data compression is performed once, one picture is constructed by image data composed of a plurality of frames, the constructed picture is stored temporarily in the image memory, the image data that has been stored in the image memory is compressed and the compressed image data is then recorded on the recording medium. As a result, data compression processing for image data of a plurality of frames need be performed only one time. This makes possible rapid-sequence photography at high speeds.